Defoaming agent and/or deaerator for aqueous media tending to foam

ABSTRACT

A defoaming agent and/or deaerator for aqueous foamable media based on oil-in-water dispersions. The oil phase contains at least one compound from fatty alcohols, fatty acid monoglycerides, diglycerides, and triglycerides, fatty acid ester of fatty acids and monovalent to trivalent alcohols, 3-thiaalkane-1-ole, 3-thiaoxide alkane-1-ole, 3-thiadioxide-alkane-ole, and thiaalkane esters in combination with
         (i) at least one polyglycerine that is obtained by esterification of at least 20 percent of polyglycerine with 12 to 36 C carboxylic acid, and   (ii) at least one bisamide consisting of ethylene diamine and 10 to 36 C atom carboxylic acids, while the aqueous phase thereof contains at least one stabilizer, water, and an optional thickener, for aqueous media that tend to foam. Also disclosed are methods of controlling foam by adding the dispersions to a process, particularly during cellulose boiling, cellulose washing, grinding of paper pulp, paper production, and dispersion of pigments used for paper production.

The present invention relates to antifoams and/or deaerators based onoil-in-water dispersions whose oil phase contains at least onehydrophobic compound and whose aqueous phase contains at least onestabilizer, water and, if required, a thickener, for aqueous media whichtend to form foam, and to the use of the antifoams and/or deaerators forfoam control of aqueous media which tend to form foam, in particular forfoam control in pulp cooking, pulp washing, the beating of paper stock,papermaking and the dispersing of pigments for papermaking.

DE-A-30 01 387 discloses aqueous emulsifier-containing oil-in-wateremulsions which contain aliphatic alcohols having relatively highmelting points and hydrocarbons which are liquid at room temperature.The oil phase of the oil-in-water emulsions can, if required, alsocontain further components acting as antifoams, for example nonaromatichydrocarbons, fatty acids or derivatives thereof having relatively highmelting points, for example fatty acid esters, beeswax, Carnauba wax,Japan wax and montan wax.

EP-A-0 531 713 discloses antifoams based on oil-in-water emulsions whoseoil phase contains an alcohol of at least 12 carbon atoms, fatty acidesters of alcohols of at least 22 carbon atoms and C₁- to C₃₆-carboxylicacids, or fatty acid esters of C₁₂- to C₂₂-carboxylic acids withmonohydric to trihydric C₁- to C₁₈-alcohols or a hydrocarbon having aboiling point above 200° C. or fatty acids of 12 to 22 carbon atoms incombination with polyglyceryl esters which are obtainable by at least20% esterification of polyglycerol mixtures with at least one fatty acidof 12 to 36 carbon atoms. These oil-in-water emulsions, too, arestabilized with the aid of a water-soluble emulsifier.

EP-A-0 662 172 discloses antifoams based on oil-in-water emulsions,which are used, for example, as antifoams in paper mills and which arestill sufficiently effective even at relatively high temperatures of thewater circulations. Such antifoams contain, in the oil phase,

-   (a) fatty acid esters of C₁₂- to C₂₂-carboxylic acids with    monohydric to trihydric C₁- to C₂₂-alcohols,-   (b) polyglyceryl esters which are obtainable by at least 20%    esterification of polyglycerols which have at least 2 glycerol units    with at least one C₁₂- to C₃₆-fatty acid and-   (c) fatty acid esters of C₁₂- to C₂₂-carboxylic acids and    polyalkylene glycols, the molar mass of the polyalkylene glycols    being up to 5 000 g/mol. The hydrophobic phase can, if required,    contain further components, such as alcohols of at least 12 carbon    atoms or hydrocarbons having a boiling point above 200° C. These    oil-in-water emulsions are likewise stabilized with the aid of an    emulsifier.

EP-A-0 732 134 discloses antifoams and/or deaerators based onoil-in-water emulsions for aqueous media which tend to form foam, theoil phase of the emulsions containing

-   (a) at least one alcohol of at least 12 carbon atoms, distillation    residues which are obtainable in the preparation of alcohols having    a relatively high number of carbon atoms by oxo synthesis or by the    Ziegler process, or mixtures of said compounds, and-   (b) at least one ester of a sugar alcohol having at least 4 OH    groups or at least 2 OH groups and at least one intramolecular ether    bond and a fatty acid of at least 20 carbon atoms in a molar ratio    of 1 to at least 1, it being possible for some or all of the free OH    groups of these esters to be esterified with C₁₂- to C₁₈-carboxylic    acids.

The hydrophobic phase can, if required, contain further antifoamcompounds, such as fatty acid esters of alcohols of at least 22 carbonatoms and C₁- to C₃₆-carboxylic acids, polyethylene waxes, naturalwaxes, hydrocarbons having a boiling point above 200° C. or fatty acidsof 12 to 22 carbon atoms.

U.S. Pat. No. 4,950,420 discloses antifoams for the paper industry whichcontain from 10 to 90% by weight of a surface-active polyether, such aspolyalkoxylated glycerol or polyalkoxylated sorbitol, and from 10 to 90%by weight of a fatty acid ester of polyhydric alcohols, such as mono- ordiesters of fatty acids and polyethylene glycol and/or polypropyleneglycol, the antifoams being free of any oils, amides, hydrophobic silicaor silicones.

WO-A-00/44470 discloses antifoams and/or deaerators based onoil-in-water dispersions, which contain, in the hydrophobic oil phase,3-thiaalkan-1-ols, 3-thiaoxoalkan-1-ols, 3-thiadioxoalkan-1-ols, estersof said compounds or mixtures thereof as antifoam or deaeratingcompounds.

WO-A-94/20680 discloses aqueous dispersions which can be used asantifoams and ethylenebisstearamide or other aliphatic diamides togetherwith at least one compound from the group-consisting of the mono- anddiesters of polyethylene glycol and fatty acids, sulfonated mineral oilsand ethoxylation products of alcohols of 10 to 14 carbon atoms.

Most known antifoam systems have the disadvantage that their action isoften insufficient at elevated temperatures, for example above 50° C.,or considerable amounts have to be used in order to achieve sufficientdegassing and/or defoaming during the continuous papermaking process.

It is an object of the present invention to provide antifoams and/ordeaerators for aqueous media which tend to form foam, which antifoamsand/or deaerators are to have sufficient efficiency in particular atabove 50° C. even when metered in the otherwise usual amounts.

We have found that this object is achieved, according to the invention,by antifoams and/or deaerators based on oil-in-water dispersions whoseoil phase contains at least one compound from the group consisting ofthe alcohols of at least 12 carbon atoms, alkoxylated fatty alcohols,mono-, di- and triglycerides of fatty acids, fatty acid esters ofcarboxylic acids of at least 12 carbon atoms and monohydric totetrahydric alcohols of 1 to 24 carbon atoms, hydrocarbons having aboiling point above 200° C., fatty acids of 12 to 26 carbon atoms,3-thiaalkan-1-ols, 3-thiaoxoalkan-1-ols, 3-thiadioxoalkan-1-ols andesters of thiaalkane compounds and whose aqueous phase contains at leastone stabilizer, water and, if required, a thickener, if the oil-in-waterdispersions contain,

-   (i) at least one polyglyceryl ester which is obtainable by at least    20% esterification of polyglycerol with a carboxylic acid of 12 to    36 carbon atoms and-   (ii) at least one bisamide of ethylenediamine and carboxylic acids    of 10 to 36 carbon atoms.

The present invention also relates to the use of mixtures of

-   (i) at least one polyglyceryl ester which is obtainable by at least    20% esterification of polyglycerol with a carboxylic acid of 12 to    36 carbon atoms and-   (ii) at least one bisamide of ethylenediamine and carboxylic acids    of 10 to 36 carbon atoms    as an additive for antifoams and/or deaerators based on oil-in-water    dispersions, and to the use of the antifoams and/or deaerators for    foam control of aqueous media which tend to form foam, in particular    for foam control in pulp cooking, pulp washing, the beating of paper    stock, papermaking and the dispersing of pigments for papermaking.

Suitable compounds which form the hydrophobic phase of the oil-in-waterdispersions are known from the literature stated in connection with theprior art, cf. DE-A-30 01 387, EP-A-0 531 713, EP-A-0 662 172, EP-A-0732 134 and WO-A-00/44470. All compounds which are known to be antifoamsand/or deaerators, for example C₁₂- to C₄₈-alcohols, such as myristylalcohol, cetyl alcohol, stearyl alcohol, palmityl alcohol, tallow fattyalcohol and behenyl alcohol, and synthetic alcohols, for examplesaturated, straight-chain, unbranched alcohols obtainable by the Zieglerprocess by oxidation of alkylaluminums, can be used as the hydrophobicphase. Synthetic alcohols are also obtained by oxo synthesis. These areas a rule alcohol mixtures. The alcohols may contain, for example, up to48 carbon atoms in the molecule. Very effective antifoams contain, forexample, mixtures of at least one C₁₂- to C₂₆-alcohol and at least onefatty alcohol having 28 to 48 carbon atoms in the molecule, cf. EP-A-0322 830. Instead of the pure alcohols, it is also possible to use, asantifoam compounds, distillation residues which are obtainable in thepreparation of alcohols having a relatively large number of carbon atomsby oxo synthesis or by the Ziegler process. Further compounds which aresuitable as antifoams and/or deaerators are alkoxylated alcohols andalkoxylated distillation residues which are obtained in the preparationof alcohols by oxo synthesis or by the Ziegler process. The alkoxylatedcompounds are obtainable by reacting the long-chain alcohols ordistillation residues with ethylene oxide or with propylene oxide orwith a mixture of ethylene oxide and propylene oxide. Here, firstethylene oxide and then propylene oxide can be subjected to an additionreaction with the alcohols or the distillation residues or the additionreaction can be carried out first with propylene oxide and then withethylene oxide. In general, up to 5 mol of ethylene oxide or propyleneoxide undergo the addition reaction per OH group of the alcohol.Particularly preferred from the group consisting of the alkoxylatedcompounds are those reaction products which are prepared by an additionreaction of 1 or 2 mol of ethylene oxide with 1 mol of fatty alcohol ordistillation residue.

The abovementioned fatty alcohols having at least 12 carbon atoms in themolecule are generally used together with other compounds likewisehaving an antifoam action. Such compounds are, for example, fatty acidesters of C₁₂- to C₂₆-carboxylic acids, preferably of C₁₂-C₂₂-carboxylicacids, with monohydric to tetrahydric, preferably monohydric totrihydric, C₁-C₂₄-alcohols, preferably C₁-C₂₂-alcohols and morepreferably C₃-C₁₈-alcohols. The fatty acids on which these esters arebased are, for example, lauric acid, myristic acid, palmitic acid,stearic acid, arachidic acid, behenic acid, lignoceric acid and ceroticacid. Palmitic acid, stearic acid or behenic acid is preferably used.Monohydric C₁- to C₂₄-alcohols can be used for esterifying saidcarboxylic acids, e.g. methanol, ethanol, propanol, butanol, hexanol,dodecanol, stearyl alcohol and behenyl alcohol, or dihydric alcohols,such as ethylene glycol, trihydric alcohols, e.g. glycerol ortetrahydric alcohols such as for example pentaaerythritol. Trihydricalcohols such as glycerol are preferred. The polyhydric alcohols may becompletely or only partially esterified.

Further antifoam and deaerating compounds are polyglyceryl esters. Suchesters are prepared, for example, by esterifying polyglycerols whichcontain at least 2 glycerol units with at least one C₁₂- toC₃₆-carboxylic acid. The polyglycerols on which the esters are based areesterified to such an extent that compounds which are virtually nolonger soluble in water form. The polyglycerols are obtainable, forexample, by alkali-catalyzed condensation of glycerol at relatively hightemperatures or by reaction of epichlorohydrin with glycerol in thepresence of acidic catalysts. The polyglycerols usually contain from atleast 2 to about 30, preferably from 2 to 12, glycerol units. Commercialpolyglycerols contain mixtures of polymeric glycerols, for examplemixtures of diglycerol, triglycerol, tetraglycerol, pentaglycerol andhexaglycerol and, if required, polyglycerols having a higher degree ofcondensation. The degree of esterification of the OH groups of thepolyglycerols is from at least 20 to 100, preferably from 60 to 100, %.The long-chain fatty acids used for the esterification may be saturatedor ethylenically unsaturated. Suitable fatty acids are, for example,lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid,behenic acid, oleic acid, hexadecenoic acids, elaidic acid, eicosenoicacids, docosenoic acids, such as erucic acid, or polyunsaturated acids,such as octadecenedienoic acids and octadecenetrienoic acids, e.g.linoleic acid and linolenic acid, and mixtures of said carboxylic acids.Polyglyceryl esters suitable as antifoams are described, for example, inEP-A-0 662 172.

Other compounds which are suitable as antifoams and/or deaerators foraqueous media which tend to form foam, which compounds are used eitheralone or together with at least one alcohol of at least 12 carbon atoms,are esters of a sugar alcohol having at least 4 OH groups or at least 2OH groups and at least one intramolecular ether bond and a fatty acidhaving at least 20 carbon atoms in the molecule in a molar-ratio of 1 toat least 1, it being possible for some or all of the free OH groups ofthese esters to be esterified with C₁₂- to C₁₈-carboxylic acids. Estersof tetritols, pentitols and/or hexitols with fatty acids of at least 22carbon atoms in a molar ratio of 1 to at least 1.9 are preferably used.Esters of mannitol and/or sorbitol with behenic acid in a molar ratio of1 to at least 1, preferably 1 to at least 1.9, are particularlypreferably used. In addition to the suitable sugar alcohols sorbitol andmannitol, adonitol, arabitol, xylitol, dulcitol, pentaerythritol,sorbitan and erythritol are suitable. Sugar alcohols are understood asmeaning the polyhydroxy compounds which are formed from monosaccharidesby reduction of the carbonyl function and which are not themselvessugars. The anhydro compounds which form from sugar alcohols as a resultof intramolecular elimination of water may also be used. Particularlyeffective antifoams and/or deaerators are obtained when sugar alcoholsare esterified with C₂₂- to C₃₀-fatty acids. If the sugar alcohols areonly partly esterified with a fatty acid of at least 20 carbon atoms,the unesterified OH groups of the sugar alcohol can be esterified withanother carboxylic acid, for example a C₁₂- to C₁₈-carboxylic acid.Esters of this type are described in EP A-0 732 134.

The hydrophobic phase of the antifoams and/or deaerators may furthermorecontain from 1 to 100% by weight of a 3-thiaalkan-1-ol,3-thiaoxoalkan-1-ol or 3-thiadioxoalkan-1-ol, of an ester of saidcompounds or of mixtures thereof. It preferably contains from 5 to 75%by weight of a 3-thia-C₁₆- to C₃₀-alkan-1-ol, 3-thiaoxo-C₁₆- toC₃₀-alkan-1-ol or 3-thiadioxo-C₁₆- to C₃₀-alkan-1-ol or of a mixturethereof. Particularly preferred antifoams and/or deaerators are thosewhose hydrophobic phase contains from 5 to 85% by weight of a3-thia-C₁₈- to C₂₈-alkan-1-ol.

Further compounds suitable as antifoams and/or deaerators are ketoneshaving melting points above 45° C. They are generally used together withfatty alcohols whose melting points are above 40° C. Such antifoammixtures are disclosed in EP A-0 696 224. The reaction products,disclosed in DE-A 196 41 076, of, for example, mono- and/or diglycerideswith dicarboxylic acids and reaction products of glycerol withdicarboxylic acids, which reaction products are esterified with at leastone C₁₂- to C₃₆-fatty acid, are also suitable as an additive for thehydrophobic phase of the novel antifoams and/or deaerators.

Other compounds which enhance the efficiency of long-chain alcohols asantifoams and are therefore also used in antifoam mixtures are, forexample, polyethylene waxes having a molar mass of at least 2 000 andnatural waxes, such as beeswax or Carnauba wax.

A further component of antifoam mixtures comprises hydrocarbons having aboiling point above 200° C. (determined at atmospheric pressure).Preferably used hydrocarbons are liquid paraffins, for example thecommercially available paraffin mixtures, which are also referred to aswhite oil. Paraffins whose melting point is, for example, above 50° C.are also suitable.

According to the invention, the antifoams and/or deaerators contain, inthe hydrophobic phase, combinations of

-   (i) at least one polyglyceryl ester which is obtainable by at least    20% esterification of polyglycerol with a carboxylic acid of 12 to    36 carbon atoms and-   (ii) at least one bisamide of ethylenediamine and carboxylic acids    of 10 to 36 carbon atoms.

The amount of the polyglyceryl esters in the hydrophobic phase of theoil-in-water dispersions is, for example, from 0.5 to 80, preferablyfrom 2 to 20, % by weight. The weight ratio of (i) polyglyceryl estersto (ii) bisamides is, for example, from 10:1 to 1:10, preferably from3:1 to 1.5:1. Suitable polyglyceryl esters (i) have already beenmentioned above. Bisamides of ethylenediamine and carboxylic acids of 10to 36 carbon atoms are described, for example, in WO-A-94/20680.Particularly preferably used amides (ii) are ethylenebisstearamide,ethylenebisbehenamide and/or ethylenebislauramide. The oil phase of theoil-in-water dispersions preferably contains at least one fatty alcoholhaving 12 to 26 carbon atoms in the molecule, at least one glycerylester of fatty acids of 12 to 26 carbon atoms, preferably 12 to 22carbon atoms, and at least one mineral oil in combination with (i) apolyglyceryl ester and at least one bisamide (ii).

The hydrophobic phase accounts, for example, for from 5 to 60,preferably from 10 to 50, in particular from 10 to 35, % by weight ofthe oil-in-water dispersions. The amount of the aqueous phase of thedispersions is obtained therefrom in each case as the additional amountto 100% by weight, and is, for example, from 95 to 25% by weight.

The abovementioned compounds which are effective as antifoams and/ordeaerators are used, either alone or as a mixture with one another, incombination with components (i) and (ii) for the preparation of thenovel antifoam and deaerator dispersions. They may be mixed with oneanother in any desired ratio. The mixing of the compounds and also theemulsification in water are effected at relatively high temperatures.The active components which form the oil phase of the antifoam mixtureare heated, for example, to above 40° C., e.g. from 70 to 140° C., andemulsified under the action of shear forces in water, so thatoil-in-water emulsions are obtained. Commercial apparatuses are used forthis purpose. The mean particle size of the dispersed hydrophobic phaseis, for example, in general from 0.4 to 40 μm, preferably from 0.5 to 10μm.

The finely divided oil-in-water emulsions thus obtained are stabilized,for example a stabilizer is added, for example water-soluble,amphiphilic copolymers having acid groups or water-soluble salts of saidcopolymers. Here, it is possible, for example, to add from 0.01 to 3% byweight, based on the total emulsion, of a water-soluble amphiphiliccopolymer having acid groups or of a water-soluble salt thereof to theoil-in-water emulsion directly after homogenization, or to emulsify thecompounds acting as antifoams and/or deaerators in an aqueous solutionof a water-soluble, amphiphilic copolymer having acid groups or of asalt thereof. In this way, dispersions having a long shelf life areobtained after cooling to room temperature.

The novel oil-in-water dispersions can, if required, contain finelydivided, virtually water-insoluble, inert solids having particle sizesof less than 20 μm, preferably from 0.1 to 10 μm, in an amount of, forexample, from 0.1 to 50, preferably from 1 to 35, % of the weight of theoil phase of the oil-in-water dispersions. Suitable inert solids are,for example, kaolin, chalk, bentonite, talc, barium sulfate, silica,urea/formaldehyde pigments, melamine/formaldehyde pigments andmicrocrystalline cellulose. The use of said solids in antifoams isdisclosed in DE-A-36 01 929.

Antifoam dispersions which contain, as a stabilizer, from 0.01 to 3% byweight of a water-soluble, amphiphilic copolymer having acid groups orof a salt thereof are particularly advantageous.

Further advantageous antifoam dispersions contain, as a stabilizer, from0.1 to 3% by weight, based on the oil-in-water dispersions, of at leastone

-   -   polymer of monoethylenically unsaturated acids having molar        masses of from 1 500 to 300 000,    -   graft polymer of from 5 to 40 parts by weight of        N-vinylformamide on 100 parts by weight of a polyalkylene glycol        having a molar mass of from 500 to 10 000,    -   zwitterionic polyalkylenepolyamine,    -   zwitterionic polyethyleneimine,    -   zwitterionic polyetherpolyamine or    -   zwitterionic crosslinked polyalkylenepolyamine.

Antifoams and/or deaerators which contain, as a stabilizer, homopolymersof acrylic acid, homopolymers of methacrylic acid, copolymers of acrylicacid and methacrylic acid, copolymers of acrylic acid and maleic acid,copolymers of methacrylic acid and maleic acid, polyvinylsulfonic acid,polyacrylamido-2-methylpropanesulfonic acid or their alkali metal andammonium salts having molar masses of from 1 500 to 300 000 arepreferred.

However, the novel dispersions may also contain conventional nonionic,anionic, amphoteric and/or cationic emulsifiers as sole stabilizers oras coemulsifiers. They are used, for example, in amounts of from 0.01 to3% by weight for stabilizing oil-in-water dispersions. They are, forexample, customary surface-active substances which are compatible withthe other substances of the antifoam dispersion. The surface-activecompounds used as sole emulsifier or as coemulsifier with an anionicamphiphilic copolymer may also be used as a mixture with one another.For example, mixtures of anionic and nonionic surface-active substancescan be used for further stabilization of the antifoam dispersions. Thesurface-active compounds suitable as a coemulsifier are described as acomponent of antifoam formulations in the publications cited inconnection with the prior art. Such coemulsifiers are, for example,sodium salts or ammonium salts of higher fatty acids, alkoxylatedalkylphenols, oxyethylated unsaturated oils, such as reaction productsof one mole of castor oil and from 30 to 40 mol of ethylene oxide,sulfated ethoxylation products of nonylphenol or octylphenol, and theirsodium salts or ammonium salts, alkylarylsulfonates, sulfonates ofnaphthalene and naphthalene condensates, sulfosuccinates and adducts ofethylene oxide and/or propylene oxide with fatty alcohols, polyhydricalcohols, amines or carboxylic acids. Particularly effectivecoemulsifiers are sulfated alkyldiphenyl oxides, in particularbissulfated alkyldiphenyl oxides, such as bissulfated dodecyldiphenyloxide.

If the polymeric stabilizers are not sufficiently water-soluble in theform of the free acid, they are used in the form of water-soluble salts,for example the corresponding alkali metal, alkaline earth metal andammonium salts. These salts are prepared, for example, by partial orcomplete neutralization of the free acid groups of the amphiphiliccopolymers with bases, for example sodium hydroxide solution, potassiumhydroxide solution, magnesium oxide, ammonia or amines, such astriethanolamine, ethanolamine, morpholine, triethylamine or butylamine,being used for the neutralization. The acid groups of the amphiphiliccopolymers are preferably neutralized with ammonia or sodium hydroxidesolution.

The amphiphilic copolymers contain units of

-   (a) hydrophobic monoethylenically unsaturated monomers and-   (b) monoethylenically unsaturated carboxylic acids,    monoethylenically unsaturated sulfonic acids, monoethylenically    unsaturated phosphonic acids or mixtures thereof.

Suitable hydrophobic monoethylenidally unsaturated monomers

-   (a) are, for example, styrene, methylstyrene, ethylstyrene,    acrylonitrile, methacrylonitrile, C₂- to C₁₈-olefins, esters of    monoethylenically unsaturated C₃- to C₅-carboxylic acids and    monohydric alcohols, vinyl alkyl ethers, vinyl esters or mixtures    thereof. From this group of monomers, isobutene, diisobutene,    styrene and acrylic esters, such as ethyl acrylate, isopropyl    acrylate, n-butyl acrylate and sec-butyl acrylate, are preferably    used.

The amphiphilic copolymers contain, as hydrophilic monomers,

-   (b) preferably acrylic acid, methacrylic acid, maleic acid, maleic    anhydride, itaconic acid, vinylsulfonic acid,    2-acrylamidomethylpropanesulfonic acid, acrylamidopropane-3-sulfonic    acid, 3-sulfopropyl acrylate, 3-sulfopropyl methacrylate,    styrenesulfonic acid, vinylphosphonic acid or mixtures thereof in    polymerized form.

The molar mass of the amphiphilic copolymers is, for example, from 1 000to 100 000, preferably from 1 500 to 10 000. The acid numbers of theamphiphilic copolymers are, for example, from 50 to 500, preferably from150 to 350, mg KOH/g of polymer.

Stabilizers based on amphiphilic copolymers are particularly preferred,the copolymers containing

-   (a) from 95 to 45% by weight of isobutene, diisobutene, styrene or    mixtures thereof and-   (b) from 5 to 55% by weight of acrylic acid, methacrylic acid,    maleic acid, monoesters of maleic acid or mixtures thereof    as polymerized units. Particularly preferably used copolymers are    those which contain-   (a) from 45 to 80% by weight of styrene,-   (b) from 55 to 20% by weight of acrylic acid and, if required,-   (c) additionally further monomers    as polymerized units. If required, the copolymers may contain units    of monoesters of maleic acid as further monomers (c) in the form of    polymerized units. Such copolymers are obtainable, for example, by    preparing copolymers of styrene, diisobutene or isobutene or    mixtures thereof with maleic anhydride in the absence of water and    reacting the copolymers with alcohols after the polymerization, from    5 to 50 mol % of a monohydric alcohol being used per mole of    anhydride groups in the copolymer. Suitable alcohols are, for    example, methanol, ethanol, n-propanol, isopropanol, n-butanol,    isobutanol and tert-butanol. However, the anhydride groups of the    copolymers may also be reacted with polyhydric alcohols, such as    glycol or glycerol.

However, the reaction is carried out here until only one OH group of thepolyhydric alcohol reacts with the anhydride group. If not all theanhydride groups of the copolymers are reacted with alcohols, the ringopening of the anhydride groups not reacted with alcohols is effected byadding water.

Other compounds to be used as a stabilizer are, for example, commercialpolymers of monoethylenically unsaturated acids and graft polymers ofN-vinylformamide on polyalkylene glycols, which are described, forexample, in WO-A-96/34903. If required, up to 10% of the grafted-onvinylformamide units may be hydrolyzed. The amount of grafted-onvinylformamide units is preferably from 20 to 40% by weight, based onpolyalkylene glycol. Polyethylene glycols having molar masses of from 2000 to 10 000 are preferably used.

The zwitterionic polyalkylenepolyamines and zwitterionicpolyethyleneimines also suitable as stabilizers are disclosed, forexample, in EP-B-0112592. Such compounds are obtainable, for example, byfirst alkoxylating a polyalkylenepolyamine or polyethyleneimine, forexample with ethylene oxide, propylene oxide and/or butylene oxide, andthen quaternizing the alkoxylation products, for example with methylbromide or dimethyl sulfate, and then sulfating the quaternized,alkoxylated products with chlorosulfonic acid or sulfur trioxide. Themolar mass of the zwitterionic polyalkylenepolyamines is, for example,from 1 000 to 9 000, preferably from 1 500 to 7 500. The zwitterionicpolyethyleneimines preferably have molar masses of from 2 000 to 1 700Dalton.

The aqueous phase can, if required, contain a thickener, for examplehigh molecular weight polymers having an average molar mass Mw of morethan 1 million. Such thickeners for oil-in-water antifoam mixtures aredisclosed, for example, in EP-A-0 142 812. They are, for example,polyacrylamides, polyacrylic acids or copolymers of acrylic acid withacrylamide.

The novel antifoams and/or deaerators are very effective in aqueoussystems which tend to foam, both at room temperature and at highertemperatures, for example at above 35° C., preferably >52° C. Comparedwith known antifoams, they have a substantially improved long-termeffect. The oil-in-water dispersions are preferably used as antifoamsand/or deaerators for foam control of aqueous media which tend to formfoam, for example in papermaking, in the food industry and the starchindustry and in wastewater treatment plants. Of particular interest,however, is the use of the antifoams and/or deaerators for foam controlin pulp cooking, pulp washing, the beating of paper stock, papermakingand the dispersing of pigments for papermaking. In these processes, thetemperature of the aqueous medium to be defoamed is in general above 50°C., for example from 52 to 75° C. The novel mixtures based onoil-in-water dispersions act both as antifoams and as deaerators. Insome cases, the deaerator effect is more pronounced than the antifoameffect. They can be used as antifoams or deaerators. They are alsoadvantageously used in engine sizing and surface sizing of paper. Whenthese mixtures are used in paper stock suspensions, for example, theirdeaerating effect is of primary importance. For example, up to 0.5,preferably from 0.002 to 0.3, % by weight, based on 100 parts by weightof paper stock, of the deaerators are used in a foam-forming medium.

In the examples which follow, parts and percentages are by weight,unless stated otherwise.

EXAMPLES

The deaerating, antifoam effect was determined with the aid of a Sonicameasuring apparatus, the amount added to a 0.42% strength paper stocksuspension at 60° C. being exactly sufficient to give a concentration of5 ppm, based on the fat phase (active substance), of antifoam. The aircontent was determined continuously by means of ultrasonic attenuationbefore the metering of the antifoam and during the first 5 minutes afterthe metering. The air content initially decreased and increased againbefore the end of the measurement. In the tables, the minimum aircontent of the paper stock suspension is stated in % by volume in eachcase. This method of measurement is described in TAPPI Journal, 71(1988), 65-69.

Said paper stock suspension was used in all examples and comparativeexamples. Before addition of a deaerator, it contained 1.6% by volume ofair. In the table, the air content in % by volume after metering of thedeaerator is stated under the heading minimum air content. The lowerthis number, the more effective is the deaerator.

The long-term effect of the antifoam or deaerator was determined bycomparing the air content of the paper stock suspension after 5 minuteswith the minimum air content (immediately after the metering of thedeaerator). The value stated in the table for the long-term effect isthe difference between the value for the deaerating effect after 5minutes and the value measured immediately after the metering. The lowerthe value, the better is the long-term effect.

The stated particle sizes are mean values which were determined with theaid of a Coulter LS 230 apparatus on about 0.01% strength dispersions.The apparatus operates according to the Fraunhofer diffractionprinciple.

The viscosities were determined in a Brookfield rotation viscometer(digital model RV TDV-II).

A Fryma colloid mill, type MZ 50/A (Fryma-Maschinenbau GmbH, D-79603Rheinfelden), was used for dispersing.

Example 1

The oil phase consisted of the following components:

19.4 parts of a fatty alcohol mixture of C₁₂- to C₂₆-alcohols

0.8 part of ethylenebisstearamide

5 parts of a glyceryl ester of C₁₂- to C₂₂-fatty acids

1.0 part of mineral oil (commercial white oil) and

2.3 parts of a polyglyceryl ester which was prepared by 75%esterification of a polyglycerol mixture of

30% of diglycerol,

42% of triglycerol,

17% of tetraglycerol and

11% of polyglycerols having a higher degree of condensation with a C₁₂-to C₂₆-fatty acid mixture.

The aqueous phase consisted of

70 parts of water

3 parts of a 35% strength by weight emulsifier which is obtainable by anaddition reaction of 25 mol of ethylene oxide with 1 mol ofisooctylphenol and esterification of the adduct with sulfuric acid togive the monoester,

0.45 part of a 31% strength water-in-oil emulsion of an anionicpolyacrylamide (sodium salt of a copolymer of 30% of acrylic acid and70% of acrylamide) and

0.3 part of a 30% strength aqueous formaldehyde solution.

The components of the oil phase were first heated to 125° C. and addedto the aqueous phase heated to 90° C., with stirring and dispersing. Theemulsion was rapidly cooled to 25° C. with constant stirring. Theresulting dispersion had a viscosity of 560 mPa·s and a mean particlesize of 3.05 μm.

Comparative Example 1

The oil phase consisted of the following components:

20.2 parts of a fatty alcohol mixture of C₁₂- to C₂₆-alcohols

5 parts of a glyceryl ester of C₁₂- to C₂₂-fatty acids

1 part of mineral oil (commercial white oil) and

2.3 parts of a polyglyceryl ester prepared by 75% esterification of apolyglycerol mixture of

30% of diglycerol,

42% of triglycerol,

17% of tetraglycerol and

11% of polyglycerols having a higher degree of condensation with a C₁₂-to C₂₆-fatty acid mixture.

The aqueous phase consisted of

70 parts of water

3 parts of a 35% strength by weight emulsifier which is obtainable by anaddition reaction of 25 mol of ethylene oxide with 1 mol ofisooctylphenol and esterification of the adduct with sulfuric acid togive the monoester,

0.45 part of a 31% strength water-in-oil emulsion of an anionicpolyacrylamide (sodium salt of a copolymer of 30% of acrylic acid and70% of acrylamide) and

0.3 part of 30% strength aqueous formaldehyde solution.

The components of the oil phase were first heated to 125° C. and addedto the aqueous phase heated to 90° C., with stirring and dispersing. Theemulsion was rapidly cooled to 25° C. with constant stirring. Theresulting dispersion had a viscosity of 480 mPa·s and a mean particlesize of 3.15 μm.

Example 2

The oil phase comprising

22.7 parts of a mixture of 3-thia-C₂₀-C₂₈-alkan-1-ols, preparedaccording to the example for thiaalkanol A of WO-A-00/44470, page 20,

2.5 parts of a glyceryl ester of C₁₂- to C₂₂-fatty acids

0.9 part of ethylenebisstearamide

2.3 parts of a polyglyceryl ester prepared by 75% esterification of apolyglyceryl mixture of

30% of diglycerol

42% of triglycerol

17% of tetraglycerol and

11% of polyglycerols having a high degree of condensation with a C₁₂- toC₂₆-fatty acid mixture

was melted at 125° C. under an N₂ atmosphere, a homogeneous melt beingobtained. This was emulsified with the aid of a disperser in a solutionat 90° C. and comprising

1.8 parts of a 42% strength by weight aqueous ammoniacal solution of apolymer based on 50 parts by weight of styrene and 50 parts by weight ofacrylic acid (obtainable from S.C. Johnson under the name Joncryl EEC207),

0.45 part of a 31% strength by weight water-in-oil emulsion of ananionic polyacrylamide (sodium salt of a copolymer of 30% by weightacrylic acid and 70% by weight of acrylamide),

0.3 g of 30% strength aqueous formaldehyde solution and

0.04 g of 10% strength sulfuric acid and

70 g of water. A homogeneous emulsion was obtained. This emulsion wasrapidly cooled to room temperature, a dispersion being obtained (curingof the oil droplets). The mean particle size of was 2.85 μm and theviscosity 370 mPa·s.

Comparative Example 2

23.5 parts of a mixture of 3-thia-C₂₀-C₂₈-alkan-1-ols, preparedaccording to the example for thiaalkanol A of WO-A-00/44470, page 20,

2.5 parts of a glyceryl ester of C₁₂- to C₂₂-fatty acids,

2.3 parts of a polyglyceryl ester prepared by 75% esterification of apolyglycerol mixture of

30% of diglycerol,

42% of triglycerol,

17% of tetraglycerol and

11% of polyglycerols having a higher degree of condensation with a C₁₂-to C₂₆-fatty acid mixture

were melted at 125° C. under an N₂ atmosphere, a homogeneous melt beingobtained. This was emulsified with the aid of a disperser in a solutionat 90° C. and comprising

1.7 parts of a 42% strength by weight aqueous ammoniacal solution of apolymer based on 50 parts by weight of styrene and 50 parts by weight ofacrylic acid (obtainable from S.C. Johnson under the name Joncryl EEC207),

0.45 part of a 31% strength water-in-oil emulsion of an anionicpolyacrylamide (sodium salt of a copolymer of 30% of acrylic acid and70% of acrylamide),

0.04 g of 10% sulfuric acid,

0.3 g of 30% strength aqueous formaldehyde solution and

70 g of water.

A homogeneous emulsion was obtained. This emulsion was rapidly cooled toroom temperature, a dispersion being obtained (curing of the oildroplets). The mean particle size was 2.7 μm and the viscosity 330mPa·s.

Example 3

The oil phase consisted of the following components:

17.0 parts of a fatty alcohol mixture of C₁₂- to C₂₆-alcohols

2 parts of natural oil based on a glyceryl ester of C₁₂- to C₂₂-fattyacids

1.3 parts of ethylenebisstearamide

0.5 part of beeswax

4 parts of paraffin, m.p. 60/62° C.

1.8 parts of a polyglyceryl ester prepared by 75% esterification of apolyglycerol mixture of

30% of diglycerol,

42% of triglycerol,

17% of tetraglycerol and

11% of polyglycerols having a higher degree of condensation with a C₁₂-to C₂₆-fatty acid mixture.

The aqueous phase consisted of

70 parts of water,

2 parts of 45% strength sodium dodecylbenzenesulfonate,

2.1% by weight of china clay slurry (70% strength) having a meanparticle size of 1.5 μm,

0.3 part of a 31% strength water-in-oil emulsion of an anionicpolyacrylamide (sodium salt of a copolymer of 30% of acrylic acid and70% of acrylamide) and

0.3 part of 30% strength aqueous formaldehyde solution.

The components of the oil phase were first heated to 125° C. and addedto the aqueous phase at 90° C. with stirring and dispersing. Theemulsion was rapidly cooled to 25° C. with constant stirring. Theresulting dispersion had a viscosity of 780 mPa·s and a mean particlesize of 3.5 μm.

Comparative Example 3

The oil phase consisted of the following components:

18.3 parts of a fatty alcohol mixture of C₁₂- to C₂₆-alcohols,

2 parts of natural oil based on a glyceryl ester of C₁₂- to C₂₂-fattyacids,

0.5 part of beeswax,

4 parts of paraffin, m.p. 60/62° C. and

1.8 parts of a polyglyceryl ester prepared by 75% esterification of apolyglycerol mixture of

30% of diglycerol,

42% of triglycerol,

17% of tetraglycerol and

11% of polyglycerols having a higher degree of condensation with a C₁₂-to C₂₆-fatty acid mixture.

The aqueous phase consisted of

70 parts of water,

2 parts of 45% strength sodium dodecylbenzenesulfonate,

2.1% by weight of china clay slurry (70% strength) having a meanparticle size of 1.5 μm,

0.3 part of a 31% strength water-in-oil emulsion of an anionicpolyacrylamide (sodium salt of a copolymer of 30% of acrylic acid and70% of acrylamide) and

0.3 part of 30% strength aqueous formaldehyde solution.

The components of the oil phase were first heated to 125° C. and addedto the aqueous phase at 90° C. with stirring and dispersing. Theemulsion was rapidly cooled to 25° C. with constant stirring. Theresulting dispersion had a viscosity of 820 mPa·s and a mean particlesize of 3.6 μm.

Comparative Example 4

The oil phase consisted of the following components:

20.7 parts of a fatty alcohol mixture of C₁₂- to C₂₆-alcohols,

2 parts of natural oil based on a glyceryl ester of C₁₂- to C₂₂-fattyacids,

1.3 parts of ethylenebisstearamide,

0.5 part of beeswax,

4 parts of paraffin, m.p. 60/62° C., and

the aqueous phase consisting of

70 parts of water,

2 parts of 45% strength sodium dodecylbenzenesulfonate,

0.3 part of a 31% strength water-in-oil emulsion of an anionicpolyacrylamide (sodium salt of a copolymer of 30% of acrylic acid and70% of acrylamide) and

0.3 part of 30% strength aqueous formaldehyde solution.

The components of the oil phase were first heated to 125° C. and addedto the aqueous phase at 90° C. with stirring and dispersing. Theemulsion was rapidly cooled to 25° C. with constant stirring. Theresulting dispersion had a viscosity of 910 mPa·s and a mean particlesize of 3.6 μm.

The oil-in-water dispersions prepared according to the examples andcomparative examples were tested by the methods described above withregard to their antifoam or deaerating effect when used in amounts of 5or 3 ppm, based on dry paper stock. The results are shown in the table.

TABLE Air content in % by volume with use of 5 ppm, based on dry 3 ppm,based on dry matter, of deaerator matter, of deaerator Comparativelowest average lowest average Example example value over 5 min valueover 5 min 1 — 0.40 0.68 0.83 1.02 — 1 0.85 1.1 1.01 1.22 2 — 0.38 0.750.98 1.20 — 2 0.82 1.03 1.03 1.18 3 — 0.42 0.72 0.80 1.05 — 3 0.88 1.120.98 1.21 — 4 1.01 1.23 1.10 1.22

As shown by the results of the measurements, the combination ofpolyglyceryl esters with ethylenebisstearamide has an improved effectcompared with the use of the individual components.

1. An antifoam and/or deaerator based on an oil-in-water dispersion comprising an oil phase of at least one hydrophobic compound and an aqueous phase which comprises at least one stabilizer, water and, optionally, a thickener, wherein the oil-in-water dispersion comprises a combination of component (i) at least one polyglyceryl ester which is obtained by at least 20% esterification of polyglycerol with a carboxylic acid of 12 to 36 carbon atoms and component (ii) at least one bisamide of ethylenediamine and carboxylic acids of 10 to 36 carbon atoms, wherein the hydrophobic compound is selected from the group consisting of the alcohols of at least 12 carbon atoms, mono-, di- and triglycerides of fatty acids, fatty acid esters of carboxylic acids of at least 12 carbon atoms and monohydric to tetrahydric alcohols of 1 to 24 carbon atoms, 3-thiaalkan-1-ols, 3-thiaoxoalkan-1-ols, 3-thiadioxoalkanols, esters of the thiaalkane compounds and mixtures thereof, and wherein the dispersion excludes fatty acids of 12 to 26 carbon atoms and alkoxylated fatty alcohols.
 2. An antifoam and/or deaerator as claimed in claim 1, wherein the hydrophobic compound is selected from the group consisting of the alcohols of at least 12 carbon atoms, mono-, di- and triglycerides of fatty acids, fatty acid esters of carboxylic acids of at least 12 carbon atoms and monohydric to trihydric alcohols of 3 to 22 carbon atoms, 3-thiaalkan-1-ols, 3-thiaoxoalkan-1-ols, 3-thiadioxoalkanols, esters of the thiaalkane compounds and mixtures thereof.
 3. An antifoam and/or deaerator as claimed in claim 1, wherein the weight ratio of (i) polyglyceryl esters to (ii) bisamides is from 10:1 to 1:10.
 4. An antifoam and/or deaerator as claimed in claim 1, wherein the weight ratio (i) polyglyceryl esters to (ii) bisamides is from 3:1 to 1.5:1.
 5. An antifoam and/or deaerator as claimed in claim 1, wherein the oil phase comprises at least one fatty alcohol with 12 to 26 carbon atoms in the molecule, at least one glyceryl ester of fatty acids of 12 to 26 carbon atoms and at least one mineral oil.
 6. An antifoam and/or deaerator as claimed in claim 1, wherein the amount of the hydrophobic phase of the oil phase in the composition of the oil-in-water dispersion is from 5 to 60% by weight and the amount of the aqueous phase is from 95 to 40% by weight.
 7. An antifoam and/or deaerator as claimed in claim 6, wherein the amount of the hydrophobic phase of the oil phase in the composition of the oil-in-water dispersion is from 10 to 50% by weight.
 8. An antifoam and/or deaerator as claimed in claim 6, wherein the amount of the hydrophobic phase of the oil phase in the composition of the oil-in-water dispersion is from 10 to 35% by weight.
 9. An antifoam and/or deaerator as claimed in claim 1, wherein the oil-in-water dispersion contains from 0.1 to 50% by weight of said at least one polyglyceryl ester.
 10. An antifoam and/or deaerator as claimed in claim 1, which contains ethylenebisstearamide as bisamide (ii).
 11. An antifoam and/or deaerator as claimed in claim 1, wherein the polyglycerol used to make the polyglyceryl ester is obtained from a mixture of diglycerol, triglycerol, tetraglycerol and polyglycerols having a higher degree of condensation.
 12. A method for foam control comprising adding an antifoam and/or deaerator as claimed in claim 1 to a process.
 13. A method as claimed in claim 12 wherein said process is a process for making paper.
 14. A paper made by the process as claimed in claim
 13. 15. A method as claimed in claim 12 wherein said process is pulp cooking, pulp washing, paper stock beating, papermaking and pigment dispersing.
 16. An antifoam and/or deaerator based on an oil-in-water dispersion comprising an oil phase of at least one hydrophobic compound and an aqueous phase which comprises at least one stabilizer, water and, optionally, a thickener, wherein the oil-in-water dispersion comprises a combination of component (i) at least one polyglyceryl ester which is obtained by at least 20% esterification of polyglycerol with a carboxylic acid of 12 to 36 carbon atoms and component (ii) at least one bisamide of ethylenediamine and carboxylic acids of 10 to 36 carbon atoms, wherein the hydrophobic compound is selected from the group consisting of alcohols of at least 12 carbon atoms and 3-thiaalkan-1-ols, and wherein the dispersion excludes fatty acids of 12 to 26 carbon atoms.
 17. An antifoam and/or deaerator as claimed in claim 16, wherein the hydrophobic compound comprises at least one alcohol of at least 12 carbon atoms.
 18. An antifoam and/or deaerator as claimed in claim 16, wherein the hydrophobic compound comprises at least one 3-thiaalkan-1-ol. 